Due to its low absorption of neutrons, zirconium is very useful as a container for nuclear fuel rods. There are five common isotopes of zirconium, atomic weights 90, 91, 92, 94, and 96, the abundance of which in natural zirconium is 52, 11, 17, 17, and 3%, respectively. The 90 isotope has a very low neutron absorption cross-section, and is therefore an ideal fuel rod cladding, but the 91 isotope has an absorption cross-section about 10 times that of the 90 isotope. Thus, the efficiency of a nuclear reactor can be greatly increased if the 91 isotope is removed from the zirconium used to clad the nuclear fuel. This can be accomplished by a laser isotope process in which a zirconium compound such as zirconium tetrachloride or zirconium tetrapropoxide is exposed to a laser tuned to a wavelength which is absorbed by only the 90 or the 91 isotope. The light excites only the isotope which absorbs it and only the excited isotope reacts with a scavenger to form an easily separated reaction product. While the laser isotope process can produce a pure zirconium 90 isotope, it is a very expensive process.